1. Field of the Invention
The present invention relates to a method for producing a purified transition metal compound which can be industrially used.
2. Description of the Related Arts
Transition metal compounds are useful as reaction reagents in a lot of organic synthesis reactions and catalysts, and currently widely used and investigated. Among other, specific transition metal complexes containing a group having a cyclopentadiene type anionic skeleton (so-called metallocene transition metal compounds), in particular, a compound of an early transition metal such as titanium, zirconium or the like is extremely effective as catalyst components for olefin polymerization, and development of the compounds including their utilization is widely studied.
In production of such transition metal compound, it is preferable to isolate and purify the compound obtained. When a solid transition metal compound containing impurities, which has not been purified is used as it is, there often is a reduction of activity or influence on composition distribution of the resulted polymer, which are guessed to be derived from the impurities.
In synthesis of laboratory level, the following method is often adopted: a reaction solid containing a transition metal compound is dissolved in a specific solvent or a mixed solvent composed of several solvents having different properties, and the mixture is allowed to stand still for a long period of time at normal temperature or with cooling to deposit a crystal onto the bottom or wall of a flask or the like for obtaining the intended transition metal compound of high purity. However, in the case of production on industrial scale, the above-described method in which a crystal is deposited on the inner wall of a reaction vessel, has not only a problem that taking out of the crystal is extremely difficult but also a problem that the apparatus used is injured when a crystal is taken out, therefore, industrial operation is extremely difficult.